Effect of Omeprazole on the Secretion of Intrinsicfactor, Gastric Acid And

Gut: first published as 10.1136/gut.26.6.594 on 1 June 1985. Downloaded from

Gut, 1985, 26, 594-598

Effect of omeprazole on the secretion of intrinsic factor, gastric acid and pepsin in man E KITTANG, E AADLAND, AND H SCHJ0NSBY From Medical Department B, Aker University Hospital, Oslo, Norway.

SUMMARY The effect of an intravenous infusion of omeprazole (0.35 mg/kg) and placebo on basal and stimulated (pentagastrin 1.0 ,ug/kg/h) secretion of gastric acid, intrinsic factor and pepsin was studied in 10 healthy male subjects. Omeprazole caused a marked inhibition of basal and stimulated acid output. The inhibition of pepsin output was less marked, but also significant. The output of intrinsic factor, however, showed no significant change. The results indicate that acid and intrinsic factor might have different secretory mechanisms within the parietal cell.

Omeprazole (5-methoxy-2(((4-methoxy-3.5- Committee at Aker University Hospital, Oslo, dimethyl-2-pyrydinyl)-methyl)sulphinyl)-lH- Norway. benzimidazole), which is the most effective of the The gastric acid concentration was measured by substituted benzimidazoles, is a potent inhibitor of titration with 0-1 M NaOH to pH 7.4 using an acid secretion in isolated parietal cells,' isolated automatic titrator (Radiometer, Copenhagen, gastric glands,2 as both in animals3 and in man.45 Denmark). These drugs inhibit gastric acid secretion by a Aliquots of the gastric juice were depepsinised by mechanism different from antisecretagogues known adjusting the pH to 10 with 1M NaOH. After 30 http://gut.bmj.com/ so far, and studies have provided evidence that minutes the pH was adjusted to 7-0 with 1 M NaOH omeprazole inhibits the enzyme H+K+-ATP-ase,6 7 and stored at -20'C.'8 which is suggested to be the proton pump of the The intrinsic factor concentration was measured parietal cell.g-9 by the method of Gottlieb using intrinsic factor Intrinsic factorl as well as gastric acid is secreted antibody from patients with pernicious anaemia.19 by the parietal cell. Inhibitors of gastric acid The concentration of intrinsic factor in the gastric secretion such as histamine H2 receptor was in where 1 unit is the juice expressed U/ml, on September 25, 2021 by guest. Protected copyright. antagonists1-13 as well as atropine14 have been amount of intrinsic factor bound to 1 ng shown to reduce intrinsic factor secretion. Whether 57co-cyanocobalamin. The variation of duplicates or not omeprazole inhibits intrinsic factor secretion in the assay was found to be 1.78%±0-22% (mean is, however, not known. variation coefficient ±SD), and the between assay The present investigation was undertaken to variation coefficient 11 8%. The samples from the measure the effect of omeprazole on acid and omeprazole and the placebo experiments were intrinsic factor secretion. The effect of omeprazole analysed in the same batch. on pepsin secretion was also measured, since Pepsin concentration was measured by the previous studies have shown different results.15-17 method of Berstad20 using human haemoglobin as substrate, and samples with pH exceeding 6-0 were Methods excluded from the statistical analysis of the pepsin data. SUBJECTS The samples for pepsin and gastric acid Ten healthy male volunteers (mean age 26 years, determination were kept refrigerated until analysed. range 21-37 years) gave written informed consent to Aliquots containaing 61*3 mg omeprazole the study. The study was approved by the Ethical dissolved in 6-13 g polyethylenglycol (MW 400) were stored at -20°C until used. Before use omeprazole was diluted in 6-7 mmol/l NaHCO3 to Address for correspondence: Dr E Kittang, Medical Department B, Aker a final concentration of 4 mg/ml. 6 13 g Hospital, Oslo, Norway. polyethylenglycol diluted in 6-7 mmol/l NaHCO3 Received for publication 13 July 1984 was used as placebo. 594 Gut: first published as 10.1136/gut.26.6.594 on 1 June 1985. Downloaded from

Omeprazole on the secretion of intrinsic factor, gastric acid and pepsin in man 595

PROCEDURE Pentagastrin (1Oglkg / h)

The subjects fasted overnight. At 8 am a gastric tube - 120 was positioned with its tip in the distal part of the E 100 stomach under fluoroscopic control. The subjects E swallowed 200 ml of water, and the contents of the lI c 80 stomach were immediately aspirated. Omeprazole .2 -- 0-35 mg/kg or placebo was infused intravenously for 6 60 I, YI --r-j-1 five minutes in a double blind manner. One hour 0 -- Cc 40- T later an intravenous infusion of pentagastrin 0 -9 (Peptavlon, ICI, Pharmaceuticals Division, .' 20 Cheshire, UK) at a dose of 1-0 ,ug/kg/h was started I "I, and continued for 90 minutes. The gastric juice was 0 aspirated by continuous suction, and collected on ice ® 12 in 15 minute portions. Outputs of intrinsic factor and acid were calculated from measurements carried E10 out in aspirates obtained during the 60 minute basal Lfl period and the 90 minute period when pentagastrin E was infused. The pepsin data were calculated from E 6 the last 60 minutes with pentagastrin. Before and after termination of the experiments, PS- 4 blood and urine samples were taken for routine laboratory tests. (Blood: ESR, Hb, Hct, RBC, 2- WBC, differential count, thrombocytes, ASAT, ALAT, alkaline phosphatase, bilirubin, Na+, K+, Cl-, Ca2 , creatinine, bicarbonate. Urine: glucose, 15 minute periods protein, haemoglobin and microscopy). Omeprazole was well tolerated as no significant Fig. 1 Effect of iv omeprazole 0 35 mglkg on basal and changes were observed in laboratory values. Neither pentagastrin stimulated acid concentration (a), and acid output (b). Arrows indicate when omeprazole orplacebo http://gut.bmj.com/ were any side effects because of omeprazole seen or were infused. The results are shows as mean ± SEM. reported by the subjects. (o-0---o omeprazole, * * placebo). The results were presented as mean values and SEM. A paired Wilcoxon's ranked sum test was used for statistical analyses, and p values <0-05 were regarded as significant. PEPSIN SECRETION In the basal period omeprazole caused a marked rise Results in pH in gastric juice that exceeded 6 in several on September 25, 2021 by guest. Protected copyright. samples. As pepsin is irreversibly degraded at pH above 6,21 the pepsin data from the basal period ACID SECRETION were considered unreliable and was excluded from Both basal and pentagastrin stimulated gastric acid the statistical analyses. During pentagastrin output was significantly inhibited by omeprazole. stimulation mean pepsin output decreased from (Figure 1 b). The inhibition of basal acid output 125*3 mg±7*9 mg (placebo) to 79 6 mg±6-3 mg increased subsequently during the whole basal after omeprazole (p<0-01) whereas the mean pepsin period, indicating that the inhibition recorded was concentration increased from 413 mg/1±34 mg/l not maximal. The inhibition of stimulated acid (placebo) to 817 mg/1±189 mg/l after omeprazole output was 74-1%±5-2% (mean ±SEM; p<0-01), (p<001; Figure 3 a, b). and was because of a significant inhibition of both H+ concentrations (mean inhibition 39*0%±9 3%; Discussion Figure 1 a), and volumes of gastric juice (mean inhibition 59 1%±4*6%). The potent inhibitory effect of omeprazole on acid secretion was confirmed in the present study when INTRINSIC FACTOR SECRETION stimulating the secretion with a submaximal dose of Both basal and stimulated concentration of intrinsic pentagastrin (1-0 ,ug/kg/h; Fig 1 a,b). The output of factor was higher after omeprazole infusion than intrinsic factor was unchanged after omeprazole after placebo, whereas the output of intrinsic factor (Table, Fig 2 b). The concentration of intrinsic did not significantly change (Figure 2 a, b; Table). factor in the gastric juice increased, probably Gut: first published as 10.1136/gut.26.6.594 on 1 June 1985. Downloaded from

596 Kittang, Aadland, and Schjonsby Table Basal and pentagastrin (Pg) stimulated intrinsic factor concentration and intrinsic factor output after an intravenous infusion ofomeprazole andplacebo (Mean ±SEM) (ns = not significant) Intrinsicfactor concentration (Ulml) Cumulative intrinsic factor output Basal Pg Basal (U160 min) Pg (U190 min) Omeprazole 41-0±4-1 82-4±18-5 2479±540 13719±3172 Placebo 28-1±0-5 42-6±13-5 3239±836 16424±2051 p <0.01 <0-01 ns ns

because of reduced volume secretion. Hence, the in the secretory membrane of the parietal cell,6 7 and results show that omeprazole, at a dose causing appears as such to be a peripherial step in the marked inhibition of acid secretion, has no effect on secretory mechanism of hydrochloric acid. The basal and pentagastrin stimulated intrinsic factor different effect of omeprazole on acid and intrinsic secretion. The effect of maximal doses of factor secretion therefore support the hypothesis omeprazole on intrinsic factor secretion is, however, that acid and intrinsic factor have separate secretory not known. mechanisms in the parietal cell. As the parietal cell is the site of both acid and Intrinsic factor is essential for normal absorption intrinsic factor production,10 the different effect of of vitamin B12. One might therefore expect that omeprazole on intrinsic factor and acid secretion is omeprazole treatment should be without effect on of interest. It is known that omeprazole interacts absorption of vitamin B12. Nevertheless it has been with the enzyme H+K+-ATP-ase, which is located proposed that achlorhydria or hypochlorhydria

Pentogastrin (10,ug/kg/h I -a Pentagastrin (1 O0g/kg/h ) 12 r II http://gut.bmj.com/ n 160 'n 10 - 120 8- l 1 ,A-L---1~~~---l - ] .- j80 1 ? 61 I on September 25, 2021 by guest. Protected copyright. ~0 .4 Ic '1 O-J b Ui 50- G 8000 -.9 E E WIn 40- _ 6000 l 30 El-'20 0 09 u- 2000- 10 '1- -o , o. I n-9 8 6 3 6 8 9 9 9 9 1 2 3 4 5 6 7 8 9 10 15 minute periods 2 3 4 5 6 7 8 9 10 15 minute periods

Fig. 3 Effect ofiv omeprazole on basal and pentaga;strin Fig. 2 Effect ofiv omeprazole on basal andpentagastrin stimulated pepsin concentration (a) and output (b). stimulated intrinsicfactor concentration (a) and intrinsic n = number ofsamples in each period with pH <6-0. factor output (b). (Symbols as in Fig. 1.) (Symbols as in Fig. 1.) Gut: first published as 10.1136/gut.26.6.594 on 1 June 1985. Downloaded from Omeprazole on the secretion of intrinsic factor, gastric acid and pepsin in man 597 might reduce the absorption of food-bound vitamin 4 Lind T, Cederberg Ch, Ekenved G, Haglund U, Olbe B12, even in presence of sufficient amounts of L. Effect of omeprazole - a gastric proton pump intrinsic factor to ensure normal absorption of inhibitor - on pentagastrin stimulated acid secretion in unbound vitamin It has been shown that man. Gut 1983; 24: 270-6. B12.22 5 Olbe L, Haglund U, Leth R et al. Effects of substituted treatment with the histamine H2-receptor benzimidazole (H 149/94) on gastric acid secretion in antagonists cimetidine and ranitidine reduced the humans. Gastroenterology 1982; 83: 193-8. absorption of radioactive cyanocobalamin bound 6 Fellenius E, Berglindh T, Sachs G et al. Substituted to chicken serum,13 23 but has no effect on the benzimidazoles inhibit gastric acid secretion by absorption of unbound radioactive blocking (H+K+) ATP-ase. Nature 1981; 290: 159-61. cyanocobalamin.23 Whether or not omeprazole 7 Wallmark B, Sachs G, Mardh S, Fellenius E. Inhibition inhibits the absorption of vitamin B12 still remains to of gastric (H+K+) ATP-ase by the substituted be investigated. benzimidazole, picoprazole. Biochim Biophys Acta The results also show a moderate inhibition of 1983; 728: 31-8. 8 Saccomani G, Helander HF, Crago S, Chang HH, pentagastrin stimulated pepsin output (Fig 3 Dailey DW, Sachs G. Characterization of gastric a,b). The inhibition of pepsin output mucosal membranes. J Cell Biol 1979; 83: 271-83. (38-2%±7.0%) was less marked than the inhibition 9 Sachs G, Chang HH, Rabon E, Schackman R, Lewin of acid output (74-1%±5-2%; p<0-01). During the M, Saccomani G. A nonelectrogenic H+ pump in pentagastrin stimulation the pepsin concentration plasma membranes of hog stomach. J Biol Chem 1976; markedly increased, probably as an effect of 251: 7690-8. reduced volume secretion. The present results are in 10 Hoedemaker PJ, Abels J, Wachters JJ, Arends A, agreement with those reported in man by Wilson et Nieweg HO. Investigation about the site of production al. 17 of Castle's gastric intrinsic factor. Lab Invest 1964; 13: 1394-9. The mechanism by which omeprazole inhibits 11 Sharp PC, Mills JG, Horton MA, Hunt RH, Vincent pepsin secretion is unknown. Fryklund et at16 found SH, Milton-Thompson GJ. Histamin H2-receptors and that omeprazole did not inhibit pepsinogen released IF secretion. Scand J Gastroenterol 1980; 15: 377-84. in isolated zymogen cells from rabbit mucosa, 12 Fielding LP, Chalmers DM, Chanarin I, Levi AJ. whereas the formation of acid in isolated parietal Inhibition of intrinsic factor secretion by cimetidine. Br cells was strongly inhibited. The inhibition of pepsin Med J 1978; 1: 818-9. secretion can therefore not be explained by direct 13 Belaiche J, Zittoun J, Marquet J, Nurit Y, Yvart J. http://gut.bmj.com/ omeprazole interaction with the pepsin producing Effect of ranitidine on intrinsic factor secretion and cells. It might be speculated whether the inhibition cobalamin absorption. Gastroenterol Clin Biol 1983; 7: 381-4. of pepsin secretion could be an effect secondary to 14 Vatn MH, Semb LS, Schrumpf E. The effect of the inhibition of acid secretion, a theory supported atropine and vagotomy on the secretion of gastric by findings that topical application of hydrochloric intrinsic factor (IF) in man. ScandJ Gastroenterol 1975; acid stimulates the secretion of pepsin in vitro24 as 10: 59-64.

well as in healthy man.25 15 Fimmel CJ, Blum AL. Dissociated response of acid and on September 25, 2021 by guest. Protected copyright. pepsin secretion to omeprazole (H 168/68), a We wish to thank Dr A Berstad for kindly substituted benzimidazole. [Abstract] Gastroenterology performing the pepsin measurements. The study 1983; 84: 1152. was AB 16 Fryklund J, Wallmark B, Larsson H. Effect of supported by Hassle, M0lndal, Sweden. omeprazole on gastric secretion in H+K+-ATP-ase and in pepsinogen-rich cell fractions from rabbit gastric mucosa. Biochem Pharmacol 1984; 33: 273-80. 17 Wilson JA, Boyd EJS, Wormsley KG. Effect of omeprazole on pentagastrin stimulated and overnight References gastric acid and pepsin. [Abstract] Gastroenterology 1983; 84: 1352. 1 Sewing K-Fr, Harms P, Schulz G, Hanneman H. 18 Grasbeck R. Physiology and pathology of vitamin B12 Effect of substituted benzimidazoles on acid secretion absorption, distribution and excretion. Adv Clin Chem in isolated and enriched guinea pig parietal cells. Gut 1960; 2: 299-366. 1983; 24: 557-60. 19 Gottlieb Ch. Rapid charcoal assay for intrinsic factor, 2 Fellinius E, Elander B, Wallmark B, Helander HF, gastric juice unsaturated B12 binding capacity, antibody Berglindh T. Inhibition of acid secretion in isolated to IF and serum unsaturated B12 binding capacity. gastric glands by substituted benzimidazoles. Am J Blood 1963; 25: 875-84. Physiol 1982; 243: G505-10. 20 Berstad A. A modified hemoglobin substrate method 3 Larsson H, Carlsson E, Junggren U et al. Inhibition of for the estimation of pepsin in gastric juice. Scand J gastric acid secretion by omeprazole in dog and rat. Gastroenterol 1970; 5: 343-8. Gastroenterology 1982; 83: 900-7. 21 Berstad A. Inactivation of human gastric pepsin by Gut: first published as 10.1136/gut.26.6.594 on 1 June 1985. Downloaded from 598 Kittang, Aadland, and Schj0nsby

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